1. Field of the Invention
The invention relates to rotor mills or impact crushers, where a rotor comprises several rotor disks made of cast steel, where the rotor disks are welded together when employed in connection with impact crushers or hammer mills, where the rotors are advantageously utilized in machines for comminuting coal, rock, or other materials.
2. Brief Description of the Background of the Invention Including Prior Art
It is known to assemble a rotor for use in an impact crusher or hammer mill from two or more metallic rotor disks which are welded to each other and have central portions or hubs serving to receive torque from a shaft. Neighboring disks are welded to each other at their peripheries, i.e., radially outwardly of the respective hubs. Reference may be had, for example, to U.S. Pat. No. 3,098,614 and to German Utility Model No. 66 01 200. Welded seams are desirable and advantageous because they lend the necessary rigidity and stability to the assembled rotor.
A drawback of welded seams which are provided at the periphery of a conventional rotor for use in a hammer mill. is that the seams are necessarily interrupted, i.e., such seams can be said to constitute relatively small portions of circumferentially complete annuli because they are interrupted in the regions of the hammers. The same holds true for the conventional rotors of impact crushers. In addition, the welding operation which involves bonding together two or more disks to form the rotor of an impact crusher takes up much time and is complex and expensive. A further drawback of conventional rotors for use in hammer mills or impact crushers is that their interrupted welded seams are located at the periphery and are thus subject to much wear and tear as a result of contact with material which is being comminuted.
The German printed Patent document laid open No. 1,808,322 discloses a rotor with circular disks having radially innermost portions welded to a drum which serves as a shaft. However, each disk is a composite structure which is assembled of several sectors and such sectors are offset relative to each other in the axial direction of the rotor. Thus, the connections between the composite disks and the shaft are not annular welded seams but rather mere fragments or small portions of ring-shaped seams. Moreover, the bonding of sectors to the shaft is a complex and time-consuming operation and the assembled rotor is often unsatisfactory due .to unacceptable eccentricity of its components. Still further, it is necessary to provide two sets of welded seams for each disk which is part of the rotor in the aforementioned Patent document.
Annular ring welding seams are furnished at the outer edges of the front faces of the hubs, in particular, in the case of large rotors as they are employed in primary breakers in view of the beat and shock loads occurring during the operation of such breakers. Annular ring welding seams disposed at the outer edges of rotors may not show the necessary strength.
The assignee of the present application has filed another application on Feb. 28, 1991 bearing Ser. No. 07/662,009 relating to a similar subject and giving details relating to problems associated with this field.
Assignee's copending application, Ser. No. 07/662,009 teaches that at least one welding seam is preferably located at outer edges of peripheral surfaces of hubs provided at rotor disks.